Comminuting tools, particularly tools which operate with rotary bodies, are subject to substantial wear. Such wear is particularly noticeable when cutting edges, cooperating with fixed anvil elements, are used to make comminuted or granulate elements from plastic material which contains a high degree of additives, for example plastic material which contains up to about 40% glass fibers, ceramic powder, or similar, pulverized material. The plastic may, for example, be of the nylon type, that is, a polyamide which contains the glass fiber or ceramic powder as a filler. It is possible also that one or more of the cutter blades become inoperative due to foreign material or due to the elements being comminuted, for example stray bits of metal, or the like.
Comminuting tools in accordance with known structures usually have single cutting blades which are soldered or brazed on a cutter body. Upon damage to the cutting elements, re-soldering or re-brazing of new cutters is complex, time and labor-intensive, and may result in a cutting element which is different from the original cutting unit which was subject to repair due to heat distortion upon re-brazing or re-soldering of new cutter blades. Additionally, the heat used in re-brazing one cutter blade may affect adjacent cutter blades, and their position as well adhesion and secure attachment to the base body, so that great care must be taken in repair of cutter units, for example by replacing a single cutting blade. The base bodies of which these tools are made are inherently expensive since originally cylindrical elements must be formed with precisely dimensioned grooves or recesses, by material removal. Repair of such tools is usually not possible by the user itself; it can be carried out ordinarily only in specific machine shops or installations particularly adapted to carrying out the required maintenance and repair.
The referenced German Patent Disclosure Document DE-OS No. 20 64 212, to which U.S. application Ser. No. 888,709 of Dec. 29, 1969 corresponds, describes a rotary cutting tool which permits exchange of defective cutting elements or cutting edge portions. This tool is designed for cutting and severing threads, yarns, and the like. The structure of the tool is complex, which, therefore, renders it expensive. This tool is so constructed that a massive tool base body has longitudinal grooves milled therein which tool body carries the axial pin or projection for connection to a rotary drive unit. The longitudinal grooves have cutter strips inserted therein which are retained in position by clamping disks located at axial end faces of the tool body. The clamping disks have a conical surface at their inner side which overlaps correspondingly inclined end portions of the cutter strips. Since the cutter strips are held in position only at their axial ends, the cutter strips must be manufactured with extremely accurate longitudinal tolerances since, otherwise, differential clamping forces will act on the respective individual cutter strips, or an elastic sealing and compensation washer or sleeves for the cutter strips must be provided at the axial ends. Such sealing sleeves at the ends limit the clamping force which can be applied on the cutter elements themselves, thus limiting the circumferential speed with which such a tool can operate. The manufacturing cost of such tool is high since the tool body as well as the clamping disks, and the additional slits which have to be provided for the cutter strips require extensive machining.